Three-phase motor systems are pervasive in many applications from general industrial machinery to automotive uses such motors used to drive electric automobiles or provide other automotive functionality, such as power steering. Three-phase motors are generally very efficient, vibrate less and last longer than a single-phase motor of the same power under similar load conditions. However, in order to operate a three-phase motor using a DC power source or a single-phase AC power source, a three-phase control signals are generated in order to control and provide power to each phase of the three-phase motor.
One common way to generate each of the three phases is generate each of the three phases by using a series of electronic switches that are switched on and off using a pulse-width modulated signal having a duty cycle or pulse density proportional to each of the three phases. For example, each of the three phases may be generated using a half-bridge switching network that is coupled to a respective phase of the three-phase motor. Accordingly, the speed of the motor may be controlled by adjusting the pulse width modulated signal on the motor. Such half-bridge switching networks are typically implemented using semiconductor switching networks such as BJTs, MOSFETs and/or IGBTs. However, because the input impedance of a motor is generally inductive, high voltage switching transients are may result from the switching action of the switching networks of phase generation circuitry. Generally, circuits such as snubber circuits containing capacitor, diodes and/or other components are used to reduce the magnitude of such voltage transients in order to avoid damage to sensitive semiconductor components and to maintain high efficiency.